1. Field of the Invention
The invention relates to an inert rendering method for preventing and/or extinguishing fires in an enclosed space (hereinafter also called the “target area”), wherein an oxygen-inhibiting gas is introduced into the target area in order to adjust a first basic level of inertion with a reduced oxygen content in comparison with natural conditions, and wherein an oxygen-inhibiting gas is further introduced in a gradual or sudden manner (in the case of a fire) into the target area in order to adjust one or more levels of inertion with a similarly reduced oxygen content. The invention relates also to a device for carrying out the method with an oxygen-measuring device in the target area and a source of an oxygen-inhibiting gas.
2. Background Art
The method and device of the kind in question are familiar in the state of the art. The effect of the so-called “inert gas extinguishing method” is mainly based on the fact that in enclosed spaces, which are only occasionally accessed by human beings or animals and the equipment of the spaces would suffer considerable damage if traditional extinguishing methods (water and foam) were applied, the fire hazard is averted by reducing the oxygen concentration in the area concerned to an average value of approximately 12 per cent by volume, at which most flammable materials no longer burn. Realms of application are electronic data processing areas, electrical control and distributing rooms, or storage areas containing high-grade goods. The extinguishing effect is based on the principle of oxygen displacement. Normal ambient air is composed of 21% oxygen, 78% nitrogen and 1% other gases. For fire extinguishing, for example, the concentration of nitrogen in the target area is further increased by introducing pure nitrogen, thus reducing the oxygen content. It is common knowledge that an extinguishing effect takes place when the oxygen content drops below a value of 15 per cent by volume. Depending on the materials stored in the particular area, a further lowering of the oxygen content to the above-mentioned 12 per cent by volume or lower may be required.
Normally, gases such as carbon dioxide, nitrogen, inert gases and mixtures thereof are used as oxygen-inhibiting gases, which are usually stored in steel cylinders in special adjacent areas. In order to flood a target area with extinguishing gas, it has been necessary up to now to store a considerable quantity of extinguishing gas, particularly for commercially used premises, such as open-plan offices and warehouses. Since the pressure of the gas cylinders is limited due to the ultimate load of the available fittings, and also since the volumetric capacity cannot be increased as desired, a considerable number of cylinders are required to make the extinguishing gases available. This fact, together with the required gas pipes and fittings, makes great demands on the ultimate load capacity and size of the storage areas. Even if the cylinders were stored in the basement, considerable structural input would be required to lay the supply lines to the target areas. In addition, correspondingly large storage areas will result in increased building and operating costs.